High pressure gear pump

ABSTRACT

A HIGH PRESSURE GEAR PUMP PROVIDED WITH A BACK PRESSURE LOADING MECHANISM CHARACTERIZED IN THAT THE BACK PRESSURE IS ECCENTRICALLY SUBJECTED TO A PAIR OF BUSHES FACING A DRIVING GEAR AND A DRIVEN GEAR, RESPECTIVELY. A PAIR OF AXIALLY MOVABLE PRESSURE PLATES ARE INSERTED BETWEEN THE BUSHES AND THE INNER WALL OF THE CASING AND FORMED WITH A PAIR OF HIGH PRESSURE CHAMBERS ARRANGED ECCENTRICALLY TOWARDS THE HIGH PRESSURE SIDE.   A HIGH PRESSURE FLUID IS ADMITTED INTO THE PAIR OF HIGH PRESSURE CHAMBERS, WHEREBY PUMP IS PREVENT FROM SEIZURE.

May 23, 1972 YAsuo AOKI HIGH PRESSURE GEAR PUMP Filed Dec. 19, 1959 F g l II M I NVENTOR.

AM K M 0 A J, 1 0 WE United States Patent Office a 3,664,777 Patented May 23, 1972 3,664,777 HIGH PRESSURE GEAR PUMP Yasuo Aoki, Yokohama-511i, Japan, assignor to Kabushiki giaisha Komatsu Seisakusho (Komatsu Ltd.), Tokyo,

apan

Filed Dec. 19, 1969, Ser. No. 886,647 Claims priority, application Japan, Dec. 26, 1968, 43/113,798 Int. Cl. F01c 19/08; F03c 3/00; F04c 27/00 US. Cl. 418-131 7 Claims ABSTRACT OF THE DISCLOSURE A high pressure gear pump provided with a back pressure loading mechanism characterized in that the back pressure is eccentrically subjected to a pair of bushes facing a driving gear and a driven gear, respectively. A pair of axially movable pressures plates are inserted between the bushes and the inner wall of the casing and formed with a pair of high pressure chambers arranged eccentrically towards the high pressure side. A high pressure fluid is admitted into the pair of high pressure chambers, whereby the pump is prevented from seizure.

This invention relates to a high pressure gear pump provided with a back pressure loading mechanism.

In general, in a high pressure gear pump, there is provided a pressure loading mechanism for getting a. good volumetric efliciency. In accordance with the prior art, a high pressure gear pump is provided with high pressure chambers constituted by a casing, two bushes and a side cover, which are arranged in the exhaust side of the pump in one axial side thereof. By virtue of the pressure loading given to fluid introduced into the high pressure chambers, a proper clearance is kept between the gears and the bushes, so as to achieve a high volumetric efiiciency. In this case, the axes of the bushes are arranged eccentrically towards the suction side. In such a construction as above, sealing means are necessary all around the bushes, so that the area required for sealing is subjected to the pressure loading, even in the suction side. This fact frequently causes such an inevitable defeet as seizure.

The primary object of this invention is to provide a high pressure gear pump prevented from such a trouble as seizure.

Briefly stated in accordance with one aspect of this invention, there is provided a high pressure gear pump comprising a casing, a driving gear and a driven gear adapted to be rotatably mounted inside the casing in mesh with each other, and interposed between a low pressure side having an inlet and a high pressure side having an outlet, four bushes inserted between four sides of the two gears and two inner side walls of the casing, respectively, whereby a low pressure fluid supplied from the inlet is converted into a high pressure fluid and exhausted through the outlet by rotating the two gears, which includes a pair of axially movable pressure plates inserted between two of the four bushes, arranged on the same side with each other, and one of the two inner side walls, the pressure plates having high pressure chambers recessed in the surfaces thereof facing the one inner side wall and arranged eccentrically towards the high pressure side, respectively, and a pair of sealing means provided between radially external surfaces of the four bushes and the inner peripheral wall of the casing on both sides of the gears, respectively, whereby the high pressure subjected to the back surfaces of the bushes is distributed in a balanced manner, and therefore, the gear pump is prevented from seizure.

The invention will be better understood and other. objects and additional advantages of the invention will become apparent upon perusal of the following description taken in connection with the drawings, in which:

FIG. 1 is a vertically axially sectional view of a high pressure gear pump embodying this invention;

FIG. 2 is a partly removed side view taken along line II--II of FIG. 1; and

FIGS. 3(A) and 3(B) are a front view and a side view of a bush comprised in the pump, respectively.

Similar numerals refer to similar parts throughout the several views.

Referring more particularly to the drawings, the preferred embodiment of this invention will now be described; however, this description will be understood to be illustrative of the invention and not as limiting it to the particular construction shown and described. A casing 11 comprises a bracket 12, a side case 13, and a cover 14 integrated by means of bolts 15. A driving gear 16 and a driven gear 17 are housed in the casing 11. Sealing means 18a and 18b are inserted between the bracket 12 and the side case 13 as well as between the side case 13 and the cover 14, respectively, for the fluid tight construction of the casing 11. The driving gear 16 is provided with a shaft 21, of which one end is extended out of the bracket 12 through an oil sealing means 22. A bush 19a is rotatably mounted on the shaft 21 between the bracket 12 and the driving gear 16. The other end of the shaft '21 and a shaft 23 of the driven gear 17 are rotatably journalled by bushes 19b, 20a and 2011, respectively. The bushes 19a, 19b, 20a and 20b are cylinders having longitudinal planes, respectively. A circumferential groove 24 is formed and extended from an edge of the plane along the three quarters of the periphery of the cylindrical external surface of each of the bushes 19a, 19b, 20a and 20b in the circumferential direction. A sealing means 25 an 26 are anchored in these grooves 24 so as to keep the space around the two gears 16 and '17 in the fluid tight condition. These sealing means 25 and '26 are not provided along the remaining quarter of the periphery of the bushes, because the bushes are pushed enough towards the suction side by the high pressure fluid in the exhausting side for omitting the sealing means along this remaining quarter. If the sealing means 25 and 26 are arranged all-round the bushes, they would be inflated towards the suction side.

The driving gear '16 is rotated externally in the clockwise direction in FIG. 2 as shown by the arrow Y, to gether with the driven gear 17 in mesh therewith inside the casing 11. A low pressure oil supplied into the casing 11 through an inlet 27 is converted into a high pressure oil, transferred to an outlet 28 and exhausted out of the casing 11 therethrough for, for example, being supplied into a hydraulic mechanism (not shown), by the actionof the rotated gears.

Although the bushes 19a and 2011 are closed on the inner side wall of the bracket 12, the bushes 19b and 20b are not closed on the inner side wall of the cover 14 but there is a space for containing a pair of axially movable segmental pressure plates 29 and 30 between the bushes 19b and 29b and the inner side wall of the cover 14. The pressure plates 29 and 30 have round high pressure chambers 31 and 32 recessed in the'sides of the pressure plates 29 and 30 opposite to the two bushes 19b and 20b and facing the cover 14, respectively. These high pressure chambers 31 and 32 are arranged eccentrically towards the high pressure side having the outlet 28 with respect to the axes O of the gears 16 and 17; there are a distance e in parallel to a line including the two centers 0 of the two gears 16 and 17 and a distance e at the right angle thereto and to the axes between the centers 0 of'the gears 16 and 117 and the centers 0 of the round high pressure chambers 31 and 32, respectively. The values of e and e are variable depending upon such factors as pressure, rotation, magnitude of the high pressure chambers, magnitude of axial clearances, pumping capacity, etc. and may be determined experimentally. By virtue of these eccentricities of the round high pressure chambers 31 and 32, a pressure loaded to the low pressure side is smaller than another pressure loaded to the high pressure side, although the round high pressure chambers 31 and 32 are expanded from the low pressure side to the high pressure side. Two sealing rings 33 and 34 are mounted along the peripheral edges of these round high pressure chambers 31 and 32 against the inner side wall of the cover 14 so as to keep the two chambers 31 and 32 in the fluid tight state. Thus, these sealing rings 33 and 34 urge the pressure plates 29 and 30 axially toward the left, as viewed in FIG. 1, even at no load when the pump is not operating, while when the pump is operating these sealing rings 33 and 34 form the only structure in addition to the fluid pressure which urges the pressure plates 29 and 30 toward the left, as viewed in FIG. 1. The two bushes 19a and a are in close contact with each other on the respective longitudinal planes thereof. The two bushes 19b and 20b are also in close contact with each other similarly to the above two bushes 19a and 20a. The sides of the pressure plates 29 and facing the bushes 19b and 2% are recessed so as to leave clearances 37 between the pressure plate 29 and the bush 1% and between the pressure plate 30 and the bush 20b. A hole 35 is composed of two semi-circular grooves formed in the longitudinal planes of the two segmental pressure plates 29 and 30 and communicated with the clearances 37 for returning oil leaked mainly out of the sides of the gears to the suction port through passage 43. The outlet 28 has a sidewise passage 38 communicated with a passage 39 which is divided into two branched passages 40 and 41 inside the cover 14, which are communicated with the high pressure chambers 31 and 32, respectively.

In operation, the driving gear 16 is externally rotated in mesh with the driven gear 17, so that a low pressure oil in the low pressure side including the inlet 27 is converted and transferred along the radially inner walls of the side case 13 towards the high pressure side including the outlet 28 in the conventional manner. A part of the high pressure oil transferred to the outlet 28 is admitted into the sidewise passage 38 and applied to the two high pressure chambers 31 and 32 through the passage 39 and the two branched passages 40 and 41. By virtue of the eccentricities of the two high pressure chambers 31 and 32 with respect to the axes of the two gears 16 and 17, respec tively, the high pressure oil supplied to the two high pressure chambers 31 and 32 acts on the two bushes 19b and 20b in such a manner that the high pressure side is more pressured than the low pressure side. There are therefore constant clearances between the bush 1% and the pressure plate 29 and between the bush 20b and the pressure plate 30. On the other hand, the clearances provided between the gears 16 and 17 and the bushes 19b and 20b, respectively, are variable depending upon pressures given by the gears and bushes, so as to balance the two pressures, whereby an excellent efliciency is yielded while avoiding such a defect as seizure. The distribution of the pressure acting on the two bushes 19b and 20b and on the low pressure side and the high pressure side may be changed by rearranging the eccentricities of the two high pressure chambers 31 and 32. Two elliptic sealing means 25 and 26 are provided along the three quarters of the cylindrical surfaces of the bushes 19a, 19b, 20a and 20b as above mentioned, whereby the high pressure oil is confined between the two sealing means 25 and 26 so as to reduce a stress acting on, for example, the bolt 15.

While a particular embodiment of the invention has been illustrated and described, modifications thereof will readily occur to those skilled in the art. It should be understood therefore that the invention is not limited to the particular construction disclosed but that the appended claims are intended to cover all modifications which do not depart from the true spirit and scope of the invention.

What is claimed as new anddesired to be secured by Letters Patent of the United States is:

1. A high pressure gear pump comprising a casing, a driving gear and a driven gear rotatably mounted inside said casing, in mesh with each other, and interposed between a low pressure side having an inlet and a high pressure side having an outlet, and four bushes inserted between four sides of said two gears and two inner side surfaces of said casing, respectively, whereby a low pressure fluid supplied from said inlet is converted into a high pressure fluid and exhausted through said outlet by rotating said two gears, axially pressing means providing a pressing action on one side of said gears between two of said four bushes at back surfaces thereof and in parallel to the axes of said two gears, and the centers of said pressing action being radially displaced from said axes, respectively, whereby the high pressure at the two back surfaces of said two bushes is distributed in a balanced manner, and therefore, the gear pump is prevented from seizure, said axially pressing means including a pair of axially movable pressure plates inserted between two of said four bushes, arranged on the same side with each other, and at one of said two inner side surfaces, said pressure plates having high pressure chambers recessed in the surfaces thereof facing said one of said two inner side surfaces and arranged eccentrically toward said high pressure side, respectively, and the latter surfaces of said pressure plates being situated directly next to said one of said two inner side surfaces, and a pair of sealing rings respectively arranged substantially entirely within said high pressure chambers along outer edges of the latter extending between said pressure plates and said one of said two inner side surfaces for maintaining said high pressure chambers in a fluid tight state, said sealing rings forming the only structure which acts in addition to the pressure of fluid in said high pressure chambers for urging said pressure plates away from said one of said two inner side surfaces and toward said two of said four bushes, whereby said sealing rings project at any time only to a small extent beyond said pressure plates into engagement with said one of said two inner side surfaces.

2. The combination of claim 1 and wherein a pair of shafts are respectively fixed to said gears and received in said bushes, said two of said four bushes completely enclosing said shafts between said gears and said pressure plate and said pressure plates being situated entirely beyond said shafts in engagement with said back surfaces of said two of said four bushes.

3. The combination of claim 1 and wherein a pair of sealing means are provided between radially external surfaces of said four bushes and the inner peripheral wall of said casing on both sides of said gears, respectively, whereby the high pressure fluid is confined between said two sealing means so as to reduce a stress acting on the casing and the like.

4. The combination of claim 3 and wherein said sealing means is circumferentially extended all-round the radially external surface of said bush except a quater thereof near to said low pressure side.

5. The combination of claim 1 and wherein said two of said four bushes have surfaces opposed to said back surfaces thereof and directly engaging said gears.

6. The combination of claim 5 and wherein said one of said two inner side surfaces of said casing is flat and said pressure plates and sealing rings forming the only elements situated between said back surfaces of said two of said four bushes and said flat inner side surface.

7. The combination of claim 6 and wherein a pair of shafts are respectively fixed to said gears and received 5 in said bushes, said two of said four bushes completely surrounding the shafts on one side of said gears and said pressure plates being situated entirely beyond said shafts in engagement with said two back surfaces of said two bushes.

References Cited UNITED STATES PATENTS 2,769,396 11/1956 Norlin 41813l 2,816,512 12/1957 Murray 4l8132 6 Murray et a] 4l8l32 Lauck 418-132 Schmiel et a1 4l8l32 Kinnamon 4l8l32 Weigert 4l8-132 CARLTON R. CROYLE, Primary Examiner J. J. VRABLIK, Assistant Examiner 

